BoilerFaultCodesIdeal J31 Fault Code
The Ideal J31 fault code means: your heat pump's internal control system has detected an electrical communication error or a fault with the motor drive board.. It appears on 1 Ideal model in our database.
Technical description: Inverter Error
What causes the Ideal J31 fault?
This fault occurs when the heat pump's internal brain loses communication with the power unit that drives the compressor. It is usually caused by a physical failure of the inverter circuit board or loose electrical connections between the main control components. Effectively, the system can no longer send the correct signals to start the heating process, leading to a complete shutdown.
This fault can be more prevalent during summer heatwaves or extreme winter cold, as the inverter board is sensitive to temperature extremes while under heavy electrical load.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the J31 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal J31 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026